Stop for electrical control apparatus



Oct. 28, 1958 D. R. GODFREY ETAL 2,357,999

STOP FOR ELECTRICAL CONTROL APPARATUS Filed Oct. 28, 1954 Fig.l.

Gears (MVENTORS wamzsses United States Patent STOP FOR ELECTRICAL CONTROL APPARATUS Donald R. Godfrey and Eugene L. Tisdel, Hickory Township, Mercer County, Sharpsville, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 28, 1954, Serial No. 465,218

3 Claims. (Cl. 192--142) This invention relates to control apparatus and more particularly to a stop mechanism associated with a trans former tap-changer.

The output voltage of a transformer is oftentimes varied by means of a tap-changer associated therewith. When a tap-changer is used, it must be capable of efiecting a change in the output voltage of the transformer without interrupting the input or output circuits of the transformer. In order to accomplish this operation under load, it is necessary to provide at least two moving contact members so that one of the moving contact members will at all times maintain an uninterrupted electrical circuit from the input to the output of the transformer. However, when the movable contact members are in engagement with ditferent stationary contact members, the current flow through these movable contact members would be excessive unless a preventive autotransformer were connected thereto.

When the tap-changer is rotated beyond its minimum and maximum position, the preventive autotransformer is connected across all of the tapped portion of the transformer windings, thus causing excessive current to flow through the preventive autotransformer. In some transformers having a tap-changer associated therewith, a stop mechanism is provided to prevent the rotation of the tapchanger beyond these minimum and maximum positions and thus prevent the preventive autotrans former from being connected across all of the tapped portion of the transformer winding which would cause damage to the transformer. However, many of these prior art stop mechanisms are not compact and of rugged construction.

An object of this invention is to provide a stop mechanism which is both rugged and compact.

Another object of this invention is to provide for so coordinating a stop mechanism with a tap-changer that the stop mechanism prevents the tap-changer from being actuated beyond its normal operating range in either a minimum or maximum direction.

A further object of this invention is to provide for preventing a motor operation of a tap-changer when the tap-changer is being manually operated.

Other objects of this invention will become apparent from the following description when taken in conjunction with the accompanying drawing, in which:

Figure 1 is a schematic diagram of apparatus and circuits illustrating this invention and in which the stop mechanism is shown in its unactuated position;

Fig. 2 is an enlarged top view of the stop disc illustrated in Fig. 1;

Fig. 3 is a view in elevation taken along the line III-- III of Fig. 2 with application of stop bar; and

Fig. 4 is a schematic diagram illustrating the apparatus of Fig. l in the actuated position.

Referring to Fig. 1, there is illustrated an autotransformer having a fixed winding 12 and a tapped winding 14, which receive energy from supply terminals 15 and 15' and supply energy to load terminals 16 and 16.

In, order to vary the amount of the tapped winding 14 that 2,857,999 Patented Oct. 28, 1958 is connected in circuit relationship with the fixed wind:- ing 12, a tap-changer 17 is electrically connected to the tap winding 14 and to the fixed winding 12 of the transformer 10. However, in order to prevent the tap-changer 17 from being actuated beyond the minimum and maxi,- mum limits of its operating range to thereby cause damage to the transformer 10, a stop mechanism 18 responsive to the positioning of the tap-changer 17 is' provided.

Referring more particularly to the tap-changer 17, it is to be noted that the tap-changer 17 includes movable contact members 22 and 24 which are actuated by either a reversible motor 26 or by a hand-operated member, specifically a hand crank 27, through suitable gearing 2 8 and 29 and a mechanical connection 35. In operation, the field winding 31 of the motor 26 is energized in accordance with the deviation of a line voltage from the regulated value. The armature of the motor 26 in turn receives energy from supply terminals 33 and 33' which have applied thereto an alternating voltage.

In operation, one end of the movable contact member 22 remains in electrical contact with a conducting ring 30, when the contact member 22 is being actuated into its various positions around the ring 30 by means of the motor 26 or the hand crank 27. As the movable contact member 22 is being actuated through its various positions, the other end of the contact member 22 engages a plurality of stationary contact members 34, 36, 38, 40, 42, 44, 46, 48' and 50, which are electrically connected to the tapped winding 14 of the transformer 10. In like manner, one end of the movable contact member 24 en gages these stationary contact members 34, 36, 38, 40, 42, 44, 46, 48 and 50, as it is actuated through its various positions. However, the other end of the movable contact member 24 during these various positions remains continually in electrical contact with the conducting ring 52.

In order to connect the tapped winding 14 so that its turns either aid or buck the turns of the fixed winding 12, a reversing switch 54 is provided. In this instance, the reversing switch 54 comprises two stationary contact members 56 and 58 which are selectively engaged by a movable contact member 60. As illustrated, the stationary contact 56 is electrically connected to one end of the tapped winding 14, and the stationary contact member 58 is electrically connected to the other end of the tapped winding 14.

For the purpose of interconnecting the fixed winding 12 with the tapped winding 14, one end of the fixed wind,- ing 12 is electrically connected to the movable contact member 60 of the selector switch 54. As can be seen from the drawing, the load terminal 16 is also electrically connected to the movable contact member 60 as well as to the stationary contact member 50 of the tapchanger 17.

As illustrated, a preventive autotransformer 62 is electrically connected to the conducting rings 30 and 52, through conductors 66 and 68, respectively, in order to prevent an excessive flow of current through the conductors 66 and 68 when these conductors are electrically connected by means of the tap-changer 17 across a portion of the tapped winding 14. The sequence of opera tion of the movable contact members 22 and 24 of the tap-changer 17, as they move through their various tapchanging positions, will be described hereinafter.

The stop mechanism 18 is provided in order to insure that the tap-changer 17 can not be actuated beyond its extreme positions of minimum and maximum output for the autotransformer 10, which action would cause damage to the preventive autotransformer 62 since it would then become connected across all of the tapped winding 14. As will be explained more fully hereinafter, the

stop mechanism 18 automatically resets itself upon actuation in the proper direction.

, The stop mechanism 13 comprises a stop disk 70 which is recessed so as to have two cam surfaces 72 and 74 and two shoulder surfaces 76 and 78. As will be explained more fully hereinafter, the shoulder surfaces, 76 and 78 cooperate with a stop bar 80 to prevent the tapchanger 17 from being actuated beyond its normal operating range in either a minimum or maximum direction. On the other hand, the cam surfaces 72 and 74 cooperate with the stop bar 80 to effect a resetting of the stop mechanism 18.

In normal operation the stop disk 70 and the tapchanger 17 are simultaneously actuated by the motor 26, the motor 26 being mechanically connected to the movable contact members 22 and 24 through the gearing 28, the stop disk 70, the mechanical connection 35, and the gearing 29. However, if it is desired to actuate the tapchanger 17 and the stop disk 70 manually, the hand crank 27 can be removed from its position as shown in solid lines in Fig. 1 and positioned on the plate member 81 as shown in dotted lines in Fig. l.

A normally biased open switch 84 is provided so as to selectively energize or deenergize the motor 26. In this instance, the switch 84 comprises stationary and movable contact members 86 and 88, respectively, a spring 90 for biasing the switch 84 to the open position, and a plate member 92 adapted to receive the pins 94 of the hand crank 27. By turning the hand crank 27 to the position shown in solid lines in Fig. 1 against the bias of the spring 90, the movable contact member 86 of the switch 84 is actuated into engagement with the stationary contact members 86, to thereby complete an energizing circuit to the motor 26. On the other hand, when the hand crank 27 is positioned as shown in Fig. 4 the switch 84 is in the open position and the motor 26 is deenergized.

In order to limit the movement of the stop disk 70 and thus prevent an actuation of the tap-changer 17 beyond its normal operating range in either a minimum or maximum direction, the stop bar 80 is disposed for cooperation with the stop disk 70. In particular, a compression spring 102, which is disposed in a recess 104 and bears against a stationary member 106, effects an actuation of the stop bar 80 into engagement with the shoulder surface 76 of the stop disk 7t) when the tapchanger 17 is actuated beyond its normal operating range in the minimum direction and into engagement with the shoulder surface 78 when the tap-changer 17 is actuated beyond its normal operating range in a maximum direction. As illustrated, the longitudinal axis of the stop bar 80 is substantially parallel with the axis of the stop disk 70 so as to obtain compactness of the stop disk 70 and the stop bar 80.

As illustrated in Fig. 3, springs 108 are disposed on either side of the stop bar 80 in order to absorb the shock of the impact as the stop bar 80 comes into contact with either the shoulder surface 76 or the shoulder surface 78. Also, as illustrated in Fig. 3, a roller 110 is mounted on the stop bar 80 for movement therewith. In practice, the roller 110 is mounted as shown in Fig. 3. However, in order to more clearly illustrate the apparatus the roller 110 is shown in Fig. 1 to the side of the stop bar 80.

In order to hold the stop bar 80 in spaced relationship with respect to the stop disk 70, as is illustrated in Fig. 1, when the tap-changer 17 is positioned in its normal operating range, another disk 112 having an axially disposed annular flange 114 is provided.

As illustrated, the roller 110 is disposed for movement on the inner surface of the annular flange 114 when the tap-changer 17 is positioned in its normal operating range. However, an opening 116 is provided in the annular flange 114 so as to release the roller 110'when roller 110 aligns with the opening 116 once the tap-changer 17 is actuated beyond its two extreme positions.

In particular, the disk 112 rotates in accordance with the positioning of the tap-changer 17 and in accordance with the positioning of the stop disk 76 so that when the tap-changer 17 is actuated beyond either of its extreme positions the roller aligns with the opening 116 in the flange 114. This action is accomplished by mechanically connecting the disk 112 to the motor 26 through bevel gears 117, a mechanical connection 118, the gearing 29, the stop disk 70, and the gearing 28.

In normal operation, that is when the tap-changer is operating over its normal range, the stop bar 80 cooperates with the hand crank 27 to hold the switch 84 in the closed position against its bias, to thus energize the motor 26. In particular, the hand crank 27 has a notch 120 therein for receiving one end of a lever 122 which is pivoted about a point 124. The other end of the lever 122 is suitably connected to a rod 125, the other end of which is suitably secured to the stop bar 80. Thus, the hand crank 27 and the members 122 and 125 comprise latch means which is disposed for actuation by the stop bar 80 and which holds the switch 84 in the closed position when the stop bar 80 is in spaced relationship with respect to the stop disk 70 as illustrated in Fig. 1.

The operation of the apparatus illustrated in Figs. 1 through 4 will now be described assuming the tap-changer 17 is operated by hand under load although the tapchanger 17 is normally motor-operated. The output voltage of the transformer 10, as it appears across the load terminals 16 and 16, is at a minimum when the movable contact members 22 and 24 of the tap-changer 17 are both in electrical contact with the stationary contact member 48, and the movable contact member 60 of the reversing switch 54 is in electrical contact with the stationary contact member 58. In order to increase the output voltage of the transformer 10, the hand crank 27 is rotated in a clockwise direction to thereby actuate the movable contact member 22 to such a position that it engages the stationary contact 46. The output voltage of the transformer 10 is further increased by rotating the hand crank 27 further in the clockwise direction to thereby actuate the movable contact member 24 so that it too makes electrical contact with the stationary contact member 46. This sequence of positioning of the movable contact members 22 and 24 is continued by rotating the crank 27 in a clockwise direction until both the movable contact members 22 and 24 are in electrical contact with the stationary contact members 34 of the tap-changer 17. Up to this position, the turns of the tapped winding 14 aid the turns of the fixed winding 12. Then the hand crank 27 is rotated further in the clockwise direction until the movable contact member 22 makes electrical contact with the stationary contact member 50. The hand crank 27 is then further rotated in a clockwise direction to actuate the movable contact member 24 so that it will make electrical contact with the stationary contact member 50, and as soon as the movable contact member 24 breaks'contact with the stationary contact member 34, the movable contact member 60 of the reversible switch 54 is actuated so as to make electrical contact with the stationary contact member 56.

With both the movable contact members 22 and 24 in electrical contact with the stationary contact member 50 and the movable contact member 60 of the reversing switch 54 in electrical contact with the stationary contact member 56, the tap-changer is in the neutral position in which the input and output voltages are substantially equal. By rotating the hand crank 27 further in the clockwise direction, the output voltage of the transformer 10 is further increased since the turns of the tapped winding 14 are now bucking the turns of the disk 70 is thereby further rotated in a clockwise direction until finally both. the movable contact members 22 and 2 of h pa e enga e h ationary 9 tact member 34.' On further rotation of the hand crank 27 in the same direction so as to actuate. the movable contact member 22 in the direction towards the stationary contact 50 the roller 11!) aligns with the opening 116 and is released therefrom. The compression spring 102 then .actuates the stop bar 80 into engagement with the shoulder surface 78 of the stop disk 70 as illustrated in Fig. 3, to thus prevent further movement of the stop disk 70 and thus. further actuation of the tap changer 17 in the same direction. Therefore, when the movable contact member 60 of the reversing switch 54 is in electrical contact with the stationary contact member 56, it is impossible toactuate the movable contact member 22 of the tap-changer 17 until it engages the stationary contact member 50 to thereby electrically connect the preventive autotransformer 62 across the tap portion of the tapped winding 14, which would cause damage to the preventive autotransformer 62.

On rotating the hand crank 27 in a counterclockwise direction to return the tap-changer 17 to its normal operating range, the stop bar 80 slides along the cam surface 74 to thus effect a resetting of the stop bar 80. This resetting occurs when the roller 110 moves up through the opening 116 in the annular flange 114 to thereby again engage the inner surface of the annular flange 114.

In order to return the output voltage of the transformer to its minimum value, the hand crank 27 'is rotated further in a counterclockwise direction until both the movable contact members 22 and 24 are in electrical contact with the stationary contact member 48 of the tapchanger 17, and the movable contact member 60 of the reversing switch 54 is in electrical contact with the stationary contact member 58. Further actuation of the movable contact member 24 so that it would engage the stationary contact member 50 of the tap-changer 17 is prevented by the stop mechanism 18.

If the movable contact member 24 were permitted to make electrical contact with the stationary contact member 50, the preventive autotransformer 62 would be electrically connected across the tap portion of the tapped winding 14, thus causing damage thereto. Such action is prevented since before the movable contact member 24 reaches the stationary contact 50 of the tap-changer 17, the roller 110 is again released through the opening 116 of the annular flange 114, to thereby permit the compression spring 102 to actuate the stop bar 80 into engagement with the shoulder surface 76 of the stop disk 70. Such an action prevents a further movement of the stop disk 70 in the same direction and also prevents a further actuation of the tap-changer 17 in the same direction.

On rotating the hand crank 27 in the clockwise direction the stop bar 80 slides along the cam surface 72 to thereby effect a resetting of the stop bar 80. In particular, the roller 110 enters the opening 116 to thereby enable the annular flange 114 to hold it in a position as illustrated in Fig. 1.

The description of the operation so far has taken into consideration what takes place when the tap-changer 17 is hand-operated and it is to be noted that when the hand crank 27 is removed from the switch 84 and placed as shown in dotted lines in Fig. l, the spring 90 actuates the switch 84 to the open position, to thereby deenergize the motor 26. Thus, it is impossible to manually operate the tap-changer 17 while the motor 26 is energized.

The stop mechanism 18 not only prevents the 'tap-' changer 17 from being actuated beyond its extreme posi- 'tions when being manually operated, but also prevents the actuation of the tap-changer 17 beyond its extreme positions when the tap-changer 17 is being motor-driven. The operation of preventing such an actuation of the tapchanger 17 beyond its extreme positions is the same as that above described when the tap changer 17 is manually operated. Of course, when motor operating the tapchanger 17 the hand crank 27 is positioned as shown in solid lines in Fig. 1, the lever 122 cooperating with the hand crank 27 to hold it in the position as shown, to thus hold the switch 84 in the closed position. How.- ever, while the stop bar is being actuated into engagement with either the shoulder surface 76 or 78 of the stop disk 70 when motor-operating the tap-changer 17, the spring effects an actuation of the switch 84 to its open position, to thereby deenergize the motor 26. Thus, the motor 26 is deenergized before the stop bar 80 engages the stop disk 70. Therefore, possible damage to the apparatus is prevented.

The apparatus embodying the teachings of this invention has several advantages. For instance, it is rugged and compact and therefore suitable for use on tapchangers of relatively large size. In addition, the apparatus is such that it is impossible to manually actuate the tap-changer 17 when the motor 26 is energized. Further, it is impossible to actuate the stop bar 80 into engagement with the stop disk 70 when the motor 26 is energized.

Since certain changes may be' made in the abovedescribed apparatus and difierent embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. In a stop mechanism, the combination comprising. a stop disk recessed so as to have a cam surface and a shoulder surface, means for effecting a rotation of the stop disk, a stop bar for limiting the movement of the stop disk, the stop bar being perpendicular to the stop disk and the longitudinal axis of the stop bar being substantially parallel with the axis of the stop disk, means for actuating the stop bar into engagement with said shoulder surface, a roller mounted for movement with the stop bar, an annular member having an opening therein, the roller being disposed for movement on the inner surface of the annular member so as to hold the stop bar in spaced relationship with respect to the stop disk, and means for effecting a rotation of said annular member in accordance with the positioning of the stop disk so that when the annular member is rotated in one direction to a predetermined position the roller aligns with the opening in the annular member and said actuating means actuates the stop bar into engagement with the said shoulder surface to thus prevent further movement of the stop disk in the same direction, and movement of the stop disk in the opposite direction effecting a sliding of the stop bar on said cam surface to thus bring the roller into engagement with the inner surface of the annular member.

2. In a system comprising a plurality of contacts movable between two predetermined limits, means for moving said contacts between said predetermined limits, a stop-mechanism for preventing the movement of said contacts beyond said predetermined limits, said stopmechanism comprising a stop-disk and a stop-bar, said stop-disk being movable in synchronism with said movable contacts and having limiting positions thereon corresponding to the said predetermined limits of movement of said movable contacts, said stop-bar being engageable with said limits on said stop-disk to prevent movement of said movable contacts beyond said predetermined lirnits, and means comprising a first member having an opening therein and a second member for engaging said first member through the opening in said first member, said means permitting engagement of said stop-bar with said stop-disk when said movable contacts reach either of said predetermined limits, said means also being operative to disengage said stop-bar 7 from said stop-disk upon movement of said movable contacts in the opposite direction from either of said predetermined limits.

3. In a system comprising a plurality of contacts movable between two predetermined limits, means for moving said contacts between said predetermined limits, mechanism for preventing movement of said contacts beyond said predetermined limits comprising a stop-disk and a stop-bar, said stop-disk being moved in synchronism with said contacts, said stop-disk comprising two limit positions which correspond to said predetermined limits of said movable contacts, means for causing said stop-bar to engage said stop-disk to prevent movement of said movable contacts beyond said predetermined limits, said means comprising a roller mounted for movement with said stop-bar and an annular member having an opening therein, said roller being disposed for movement on the inner surface of the annular member so as to hold said stop-bar in spaced relationship with respect to said stop-disk, said annular member having an opening therein through which said roller passes to permit said stopbar to engage said stop-disk when said movable contacts reach either of said predetermined limits.

References Cited in the file of this patent UNITED STATES PATENTS 484,360 Gawlay Oct. 11, 1892 1,758,161 Lee May 13, 1930 2,478,935 Moritz et a1 Aug. 16, 1949 2,677,113 Godfrey Apr. 27, 1954 2,727,613 Radkowski Dec. 20, 1955 

